Bulky split fibers having bond strength are produced by preparing a composite synthetic resin film of three layer structure having a polypropylene layer formed of a polypropylene/polyethylene blend and a polyethylene layer on either surface of the polypropylene layer, slitting and stretching the composite film to thereby form stretched tapes, and causing splitting of the stretched tapes for fibrillation. An integral article is prepared from the resultant split fibers by mixing them alone or with plant fibers and then heating at a temperature between the melting points of polyethylene and polypropylene, thereby integrating together the split fibers with each other or with the plant fibers.